Because MS-DOS is a single-process "operating system,"
asynchronous subprocesses are not available. In particular, Shell
mode and its variants do not work. Most Emacs features that use
asynchronous subprocesses also don't work on MS-DOS, including
Shell mode and GUD. When in doubt, try and see; commands that
don't work print an error message saying that asynchronous processes
aren't supported.

Compilation under Emacs with M-x compile, searching files with
M-x grep and displaying differences between files with M-x
diff do work, by running the inferior processes synchronously. This
means you cannot do any more editing until the inferior process
finishes.

Spell checking also works, by means of special support for synchronous
invocation of the ispell program. This is slower than the
asynchronous invocation on Unix.

Instead of the Shell mode, which doesn't work on MS-DOS, you can use
the M-x eshell command. This invokes the Eshell package that
implements a Unix-like shell entirely in Emacs Lisp.

When you run a subprocess synchronously on MS-DOS, make sure the
program terminates and does not try to read keyboard input. If the
program does not terminate on its own, you will be unable to terminate
it, because MS-DOS provides no general way to terminate a process.
Pressing C-c or C-BREAK might sometimes help in these
cases.

Accessing files on other machines is not supported on MS-DOS. Other
network-oriented commands such as sending mail, Web browsing, remote
login, etc., don't work either, unless network access is built into
MS-DOS with some network redirector.

Dired on MS-DOS uses the ls-lisp package where other
platforms use the system ls command. Therefore, Dired on
MS-DOS supports only some of the possible options you can mention in
the dired-listing-switches variable. The options that work are
-A, -a, -c, -i, -r, -S,
-s, -t, and -u.